In order to meet recent demands for larger image display apparatuses, thin-type matrix panels have begun to be available such as Plasma Display Panels (PDPs), electroluminescent (EL) display devices, fluorescent display tubes, and liquid crystal display devices. Among such thin-type image display apparatuses, PDPs, in particular, are very promising as direct-view image display apparatuses with larger screens.
One method for grayscale representation on a PDP is an inter-field time division method, referred to as a sub-field method. In the inter-field time division method, one field is composed of a plurality of images (hereinafter referred to as sub-fields) with different luminance weights. The sub-field method as a method for grayscale representation is an excellent technique allowing the representation of multiple levels of gray even in binary image display apparatuses such as PDPs; i.e., display apparatuses that can represent only two levels of gray, 1 and 0. The use of this sub-field method as a method for grayscale representation allows PDPs to provide image quality substantially equal to that of cathode-ray-tube type image display apparatuses.
However, for example, when a moving image in which the gradation is gradually changing is displayed, the so-called false contour is generated that is peculiar to images on a PDP. Such generation of a false contour is due to the visual characteristics of a human, a phenomenon that seems as if grayscale had been lost, in which a color different from the original color to be represented appears as a stripe. This false contour in moving images is hereinafter referred to as a dynamic false contour.
JP 2001-34223 A suggests a method for displaying moving images and an apparatus for displaying moving images using this method, in which image correction processing is performed by detecting the amount of motion and direction of an image by a block matching method for reducing dynamic false contours. In the method and apparatus for displaying moving images, dynamic false contours are reduced by applying diffusion processing to blocks (areas) of an image for which motion vector is not accurately detected.
However, the block matching method used in the foregoing method and apparatus for displaying moving images requires determining correlations between a block to be detected and a plurality of prepared candidate blocks to detect a motion vector, which necessitates many line memories and operating circuits, and adds complexity to the circuit configuration.
It is thus desired to detect the amount of motion of an image with a simple structure. It is also desired to reduce dynamic false contours based on the amount of motion of an image without using a motion vector of the image.